It's not a counterstamp in the true sense of the word (see definition below). It may have been used as a tool tag or in a game or lottery or something where a series of dimes were struck with a punch. Or someone may have just defaced it for fun. It has character though...neat find!
Countermark or Counterstamp Partial or complete over-stamping of a coin or token in order to change its value or issuing authority, or to display an advertisement, political slogan or symbol, etc. Stamping may consist of a number (value), symbol (authority), letters (advertisement or slogan), or any combination of the above.